1 /*****************************************************************************
4 ** Name: backprojectors.cpp Classes for backprojection
5 ** Programmer: Kevin Rosenberg
6 ** Date Started: June 2000
8 ** This is part of the CTSim program
9 ** Copyright (C) 1983-2000 Kevin Rosenberg
11 ** $Id: backprojectors.cpp,v 1.5 2000/07/07 15:30:59 kevin Exp $
13 ** This program is free software; you can redistribute it and/or modify
14 ** it under the terms of the GNU General Public License (version 2) as
15 ** published by the Free Software Foundation.
17 ** This program is distributed in the hope that it will be useful,
18 ** but WITHOUT ANY WARRANTY; without even the implied warranty of
19 ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 ** GNU General Public License for more details.
22 ** You should have received a copy of the GNU General Public License
23 ** along with this program; if not, write to the Free Software
24 ** Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
25 ******************************************************************************/
29 Backprojector::Backprojector (const Projections& proj, ImageFile& im, const char* const backprojName, const char* const interpName)
32 m_pBackprojectImplem = NULL;
34 initBackprojector (proj, im, backprojName, interpName);
38 Backprojector::BackprojectView (const double* const viewData, const double viewAngle)
40 if (m_pBackprojectImplem)
41 m_pBackprojectImplem->BackprojectView (viewData, viewAngle);
44 Backprojector::~Backprojector (void)
46 delete m_pBackprojectImplem;
49 // FUNCTION IDENTIFICATION
50 // Backproject* projector = selectBackprojector (...)
53 // Selects a backprojector based on BackprojType
54 // and initializes the backprojector
57 Backprojector::initBackprojector (const Projections& proj, ImageFile& im, const char* const backprojName, const char* const interpName)
59 m_nameBackproject = backprojName;
60 m_nameInterpolation = interpName;
61 m_pBackprojectImplem = NULL;
62 m_idBackproject = convertBackprojectNameToID (backprojName);
63 if (m_idBackproject == BPROJ_INVALID) {
65 m_failMessage = "Invalid backprojection name ";
66 m_failMessage += backprojName;
68 m_idInterpolation = convertInterpolationNameToID (interpName);
69 if (m_idInterpolation == INTERP_INVALID) {
71 m_failMessage = "Invalid interpolation name ";
72 m_failMessage += interpName;
75 if (m_fail || m_idBackproject == BPROJ_INVALID || m_idInterpolation == INTERP_INVALID) {
80 if (m_idBackproject == BPROJ_TRIG)
81 m_pBackprojectImplem = static_cast<Backproject*>(new BackprojectTrig (proj, im, m_idInterpolation));
82 else if (m_idBackproject == BPROJ_TABLE)
83 m_pBackprojectImplem = static_cast<Backproject*>(new BackprojectTable (proj, im, m_idInterpolation));
84 else if (m_idBackproject == BPROJ_DIFF)
85 m_pBackprojectImplem = static_cast<Backproject*>(new BackprojectDiff (proj, im, m_idInterpolation));
86 else if (m_idBackproject == BPROJ_DIFF2)
87 m_pBackprojectImplem = static_cast<Backproject*>(new BackprojectDiff2 (proj, im, m_idInterpolation));
88 else if (m_idBackproject == BPROJ_IDIFF2)
89 m_pBackprojectImplem = static_cast<Backproject*>(new BackprojectIntDiff2 (proj, im, m_idInterpolation));
90 else if (m_idBackproject == BPROJ_IDIFF3)
91 m_pBackprojectImplem = static_cast<Backproject*>(new BackprojectIntDiff3 (proj, im, m_idInterpolation));
94 m_failMessage = "Unable to select a backprojection method [Backprojector::initBackprojector]";
102 const Backprojector::BackprojectID
103 Backprojector::convertBackprojectNameToID (const char* const backprojName)
105 BackprojectID backprojID = BPROJ_INVALID;
107 if (strcasecmp (backprojName, BPROJ_TRIG_STR) == 0)
108 backprojID = BPROJ_TRIG;
109 else if (strcasecmp (backprojName, BPROJ_TABLE_STR) == 0)
110 backprojID = BPROJ_TABLE;
111 else if (strcasecmp (backprojName, BPROJ_DIFF_STR) == 0)
112 backprojID = BPROJ_DIFF;
113 else if (strcasecmp (backprojName, BPROJ_DIFF2_STR) == 0)
114 backprojID = BPROJ_DIFF2;
115 else if (strcasecmp (backprojName, BPROJ_IDIFF2_STR) == 0)
116 backprojID = BPROJ_IDIFF2;
117 else if (strcasecmp (backprojName, BPROJ_IDIFF3_STR) == 0)
118 backprojID = BPROJ_IDIFF3;
124 Backprojector::convertBackprojectIDToName (const BackprojectID bprojID)
126 const char *bprojName = "";
128 if (bprojID == BPROJ_TRIG)
129 bprojName = BPROJ_TRIG_STR;
130 else if (bprojID == BPROJ_TABLE)
131 bprojName = BPROJ_TABLE_STR;
132 else if (bprojID == BPROJ_DIFF)
133 bprojName = BPROJ_DIFF_STR;
134 else if (bprojID == BPROJ_DIFF2)
135 bprojName = BPROJ_DIFF2_STR;
136 else if (bprojID == BPROJ_IDIFF2)
137 bprojName = BPROJ_IDIFF2_STR;
138 else if (bprojID == BPROJ_IDIFF3)
139 bprojName = BPROJ_IDIFF3_STR;
146 const Backprojector::InterpolationID
147 Backprojector::convertInterpolationNameToID (const char* const interpName)
149 InterpolationID interpID = INTERP_INVALID;
151 if (strcasecmp (interpName, INTERP_NEAREST_STR) == 0)
152 interpID = INTERP_NEAREST;
153 else if (strcasecmp (interpName, INTERP_LINEAR_STR) == 0)
154 interpID = INTERP_LINEAR;
155 #if HAVE_BSPLINE_INTERP
156 else if (strcasecmp (interpName, INTERP_BSPLINE_STR) == 0)
157 interpID = INTERP_BSPLINE;
165 * name_of_interp Return name of interpolation method
168 * name = name_of_interp (interp_type)
169 * char *name Name of interpolation method
170 * int interp_type Method of interpolation
173 * Returns NULL if interp_type is invalid
177 Backprojector::convertInterpolationIDToName (const InterpolationID interpID)
179 if (interpID == INTERP_NEAREST)
180 return (INTERP_NEAREST_STR);
181 else if (interpID == INTERP_LINEAR)
182 return (INTERP_LINEAR_STR);
183 #if HAVE_BSPLINE_INTERP
184 else if (interpID == INTERP_BSPLINE)
185 return (INTERP_BSPLINE_STR);
192 // CLASS IDENTICATION
196 // Pure virtual base class for all backprojectors.
198 Backproject::Backproject (const Projections& proj, ImageFile& im, const Backprojector::InterpolationID interpType)
199 : proj(proj), im(im), interpType(interpType)
201 detInc = proj.detInc();
203 iDetCenter = (nDet - 1) / 2; // index refering to L=0 projection
204 rotInc = proj.rotInc();
211 xMin = -proj.phmLen() / 2; // Retangular coords of phantom
212 xMax = xMin + proj.phmLen();
213 yMin = -proj.phmLen() / 2;
214 yMax = yMin + proj.phmLen();
216 xInc = (xMax - xMin) / nx; // size of cells
217 yInc = (yMax - yMin) / ny;
219 if (interpType != Backprojector::INTERP_NEAREST && interpType != Backprojector::INTERP_LINEAR)
220 sys_error (ERR_WARNING, "Illegal interpType %d [selectBackprojector]", interpType);
223 Backproject::~Backproject (void)
227 Backproject::ScaleImageByRotIncrement (void)
229 for (int ix = 0; ix < nx; ix++)
230 for (int iy = 0; iy < ny; iy++)
234 void Backproject::errorIndexOutsideDetector (int ix, int iy, double theta, double r, double phi, double L, int iDetPos)
236 printf ("r=%f, phi=%f\n", r, phi);
237 errorIndexOutsideDetector (ix, iy, theta, L, iDetPos);
240 void Backproject::errorIndexOutsideDetector (int ix, int iy, double theta, double L, int iDetPos)
242 printf ("ix=%d, iy=%d\n", ix, iy);
243 printf ("theta=%f, L=%f, detInc=%f\n", theta, L, detInc);
244 printf ("proj.ndet=%d, proj.detInc=%.4f, iDetCenter=%d\n", nDet, detInc, iDetCenter);
245 printf ("xMin=%15.8f, xMax=%15.8f, xInc=%15.8f\n", xMin, xMax, xInc);
246 printf ("yMin=%15.8f, yMax=%15.8f, yInc=%15.8f\n", yMin, yMax, yInc);
247 sys_error (ERR_WARNING, "iDetPos index outside bounds: %d [backprojector]", iDetPos);
251 // CLASS IDENTICATION
255 // Uses trigometric functions at each point in image for backprojection.
258 BackprojectTrig::BackprojectView (const double* const filteredProj, const double view_angle)
260 double theta = HALFPI + view_angle; // Add PI/2 to get perpendicular angle to detector
262 double x, y; // Rectang coords of center of pixel
264 for (x = xMin + xInc / 2, ix = 0; ix < nx; x += xInc, ix++)
265 for (y = yMin + yInc / 2, iy = 0; iy < ny; y += yInc, iy++) {
266 double r = sqrt (x * x + y * y); // distance of cell from center
267 double phi = atan2 (y, x); // angle of cell from center
268 double L = r * cos (theta - phi); // position on detector
270 if (interpType == Backprojector::INTERP_NEAREST) {
271 int iDetPos = iDetCenter + nearest<int> (L / detInc); // calc'd index in the filter raysum array
273 if (iDetPos < 0 || iDetPos >= nDet) // check for impossible: index outside of raysum pos
274 errorIndexOutsideDetector (ix, iy, theta, r, phi, L, iDetPos);
276 v[ix][iy] += rotInc * filteredProj[iDetPos];
277 } else if (interpType == Backprojector::INTERP_LINEAR) {
278 double p = L / detInc; // position along detector
279 double pFloor = floor (p);
280 int iDetPos = iDetCenter + static_cast<int>(pFloor);
281 double frac = p - pFloor; // fraction distance from det
282 if (iDetPos < 0 || iDetPos >= nDet - 1) // check for impossible: index outside of raysum pos
283 errorIndexOutsideDetector (ix, iy, theta, r, phi, L, iDetPos);
285 v[ix][iy] += rotInc * ((1-frac) * filteredProj[iDetPos] + frac * filteredProj[iDetPos+1]);
291 // CLASS IDENTICATION
295 // Precalculates trigometric function value for each point in image for backprojection.
297 BackprojectTable::BackprojectTable (const Projections& proj, ImageFile& im, Backprojector::InterpolationID interpType)
298 : Backproject::Backproject (proj, im, interpType)
300 arrayR.initSetSize (nx, ny);
301 arrayPhi.initSetSize (nx, ny);
302 r = arrayR.getArray();
303 phi = arrayPhi.getArray();
305 double x, y; // Rectang coords of center of pixel
307 for (x = xMin + xInc / 2, ix = 0; ix < nx; x += xInc, ix++)
308 for (y = yMin + yInc / 2, iy = 0; iy < ny; y += yInc, iy++) {
309 r[ix][iy] = sqrt (x * x + y * y);
310 phi[ix][iy] = atan2 (y, x);
314 BackprojectTable::~BackprojectTable (void)
316 ScaleImageByRotIncrement();
320 BackprojectTable::BackprojectView (const double* const filteredProj, const double view_angle)
322 double theta = HALFPI + view_angle; // add half PI to view angle to get perpendicular theta angle
324 for (int ix = 0; ix < nx; ix++) {
325 ImageFileColumn pImCol = v[ix];
327 for (int iy = 0; iy < ny; iy++) {
328 double L = r[ix][iy] * cos (theta - phi[ix][iy]);
330 if (interpType == Backprojector::INTERP_NEAREST) {
331 int iDetPos = iDetCenter + nearest<int>(L / detInc); // calc index in the filtered raysum vector
333 if (iDetPos < 0 || iDetPos >= nDet) // check for impossible: index outside of raysum pos
334 errorIndexOutsideDetector (ix, iy, theta, r[ix][iy], phi[ix][iy], L, iDetPos);
336 pImCol[iy] += filteredProj[iDetPos];
337 } else if (interpType == Backprojector::INTERP_LINEAR) {
338 double dPos = L / detInc; // position along detector
339 double dPosFloor = floor (dPos);
340 int iDetPos = iDetCenter + static_cast<int>(dPosFloor);
341 double frac = dPos - dPosFloor; // fraction distance from det
342 if (iDetPos < 0 || iDetPos >= nDet - 1)
343 errorIndexOutsideDetector (ix, iy, theta, r[ix][iy], phi[ix][iy], L, iDetPos);
345 pImCol[iy] += ((1-frac) * filteredProj[iDetPos] + frac * filteredProj[iDetPos+1]);
352 // CLASS IDENTICATION
356 // Backprojects by precalculating the change in L position for each x & y step in the image.
357 // Iterates in x & y direction by adding difference in L position
359 BackprojectDiff::BackprojectDiff (const Projections& proj, ImageFile& im, Backprojector::InterpolationID interpType)
360 : Backproject::Backproject (proj, im, interpType)
362 // calculate center of first pixel v[0][0]
363 double x = xMin + xInc / 2;
364 double y = yMin + yInc / 2;
365 start_r = sqrt (x * x + y * y);
366 start_phi = atan2 (y, x);
371 BackprojectDiff::~BackprojectDiff()
373 ScaleImageByRotIncrement();
377 BackprojectDiff::BackprojectView (const double* const filteredProj, const double view_angle)
379 double theta = - view_angle; // add half PI to view angle to get perpendicular theta angle
380 double det_dx = xInc * sin (theta);
381 double det_dy = yInc * cos (theta);
382 double lColStart = start_r * cos (theta - start_phi); // calculate L for first point in image
384 for (int ix = 0; ix < nx; ix++, lColStart += det_dx) {
385 double curDetPos = lColStart;
386 ImageFileColumn pImCol = v[ix];
388 for (int iy = 0; iy < ny; iy++, curDetPos += det_dy) {
390 printf ("[%2d,%2d]: %8.5lf ", ix, iy, curDetPos);
392 if (interpType == Backprojector::INTERP_NEAREST) {
393 int iDetPos = iDetCenter + nearest<int>(curDetPos / detInc); // calc index in the filtered raysum vector
395 if (iDetPos < 0 || iDetPos >= nDet) // check for impossible: index outside of raysum pos
396 errorIndexOutsideDetector (ix, iy, theta, curDetPos, iDetPos);
398 pImCol[iy] += filteredProj[iDetPos];
399 } else if (interpType == Backprojector::INTERP_LINEAR) {
400 double detPos = curDetPos / detInc; // position along detector
401 double detPosFloor = floor (detPos);
402 int iDetPos = iDetCenter + static_cast<int>(detPosFloor);
403 double frac = detPos - detPosFloor; // fraction distance from det
404 if (iDetPos < 0 || iDetPos >= nDet - 1)
405 errorIndexOutsideDetector (ix, iy, theta, curDetPos, iDetPos);
407 pImCol[iy] += ((1-frac) * filteredProj[iDetPos] + frac * filteredProj[iDetPos+1]);
414 // CLASS IDENTICATION
418 // Optimized version of BackprojectDiff
421 BackprojectDiff2::BackprojectView (const double* const filteredProj, const double view_angle)
423 double theta = - view_angle; // add half PI to view angle to get perpendicular theta angle
425 // Distance betw. detectors for an angle given in units of detectors
426 double det_dx = xInc * sin (theta) / detInc;
427 double det_dy = yInc * cos (theta) / detInc;
429 // calculate detPosition for first point in image (ix=0, iy=0)
430 double detPosColStart = start_r * cos (theta - start_phi) / detInc;
433 printf ("start_r=%8.5f, start_phi=%8.5f, rotInc=%8.5f\n", start_r, start_phi, rotInc);
435 for (int ix = 0; ix < nx; ix++, detPosColStart += det_dx) {
436 double curDetPos = detPosColStart;
437 ImageFileColumn pImCol = v[ix];
439 for (int iy = 0; iy < ny; iy++, curDetPos += det_dy) {
441 printf ("[%2d,%2d]: %8.5f %8.5f\n", ix, iy, curDetPos, filteredProj[iDetCenter + nearest<int>(L))]);
443 if (interpType == Backprojector::INTERP_NEAREST) {
444 int iDetPos = iDetCenter + nearest<int> (curDetPos); // calc index in the filtered raysum vector
446 if (iDetPos < 0 || iDetPos >= nDet) // check for impossible: index outside of raysum pos
447 errorIndexOutsideDetector (ix, iy, theta, curDetPos, iDetPos);
449 *pImCol++ += filteredProj[iDetPos];
450 } else if (interpType == Backprojector::INTERP_LINEAR) {
451 double detPosFloor = floor (curDetPos);
452 int iDetPos = iDetCenter + static_cast<int>(detPosFloor);
453 double frac = curDetPos - detPosFloor; // fraction distance from det
454 if (iDetPos < 0 || iDetPos >= nDet - 1)
455 errorIndexOutsideDetector (ix, iy, theta, curDetPos, iDetPos);
457 *pImCol++ += ((1-frac) * filteredProj[iDetPos] + frac * filteredProj[iDetPos+1]);
463 // CLASS IDENTICATION
464 // BackprojectIntDiff2
467 // Integer version of BackprojectDiff2
470 BackprojectIntDiff2::BackprojectView (const double* const filteredProj, const double view_angle)
472 double theta = - view_angle; // add half PI to view angle to get perpendicular theta angle
474 kint32 scale = 1 << 16;
475 double dScale = scale;
476 kint32 halfScale = scale / 2;
478 kint32 det_dx = nearest<kint32> (xInc * sin (theta) / detInc * scale);
479 kint32 det_dy = nearest<kint32> (yInc * cos (theta) / detInc * scale);
481 // calculate L for first point in image (0, 0)
482 kint32 detPosColStart = nearest<kint32> (start_r * cos (theta - start_phi) / detInc * scale);
484 for (int ix = 0; ix < nx; ix++, detPosColStart += det_dx) {
485 kint32 curDetPos = detPosColStart;
486 ImageFileColumn pImCol = v[ix];
488 for (int iy = 0; iy < ny; iy++, curDetPos += det_dy) {
489 if (interpType == Backprojector::INTERP_NEAREST) {
490 int detPosNearest = (curDetPos >= 0 ? ((curDetPos + halfScale) / scale) : ((curDetPos - halfScale) / scale));
491 int iDetPos = iDetCenter + detPosNearest; // calc index in the filtered raysum vector
493 if (iDetPos < 0 || iDetPos >= nDet) // check for impossible: index outside of raysum pos
494 errorIndexOutsideDetector (ix, iy, theta, curDetPos, iDetPos);
496 *pImCol++ += filteredProj[iDetPos];
497 } else if (interpType == Backprojector::INTERP_LINEAR) {
498 kint32 detPosFloor = curDetPos / scale;
499 kint32 detPosRemainder = curDetPos % scale;
500 if (detPosRemainder < 0) {
502 detPosRemainder += scale;
504 int iDetPos = iDetCenter + detPosFloor;
505 double frac = detPosRemainder / dScale;
506 if (iDetPos < 0 || iDetPos >= nDet - 1)
507 errorIndexOutsideDetector (ix, iy, theta, curDetPos, iDetPos);
509 *pImCol++ += ((1.-frac) * filteredProj[iDetPos] + frac * filteredProj[iDetPos+1]);
515 // CLASS IDENTICATION
516 // BackprojectIntDiff3
519 // Highly optimized version of BackprojectIntDiff2
522 BackprojectIntDiff3::BackprojectView (const double* const filteredProj, const double view_angle)
524 double theta = - view_angle; // add half PI to view angle to get perpendicular theta angle
525 static const int scaleShift = 16;
526 static const kint32 scale = (1 << scaleShift);
527 static const double dScale = scale;
528 static const kint32 halfScale = scale / 2;
530 const kint32 det_dx = nearest<kint32> (xInc * sin (theta) / detInc * scale);
531 const kint32 det_dy = nearest<kint32> (yInc * cos (theta) / detInc * scale);
533 // calculate L for first point in image (0, 0)
534 kint32 detPosColStart = nearest<kint32> ((start_r * cos (theta - start_phi) / detInc + iDetCenter) * scale);
536 for (int ix = 0; ix < nx; ix++, detPosColStart += det_dx) {
537 kint32 curDetPos = detPosColStart;
538 ImageFileColumn pImCol = v[ix];
540 for (int iy = 0; iy < ny; iy++, curDetPos += det_dy) {
541 if (interpType == Backprojector::INTERP_NEAREST) {
542 int iDetPos = (curDetPos + halfScale) >> scaleShift;
544 if (iDetPos < 0 || iDetPos >= nDet) // check for impossible: index outside of raysum pos
545 errorIndexOutsideDetector (ix, iy, theta, curDetPos, iDetPos);
547 *pImCol++ += filteredProj[iDetPos];
548 } else if (interpType == Backprojector::INTERP_LINEAR) {
549 kint32 detPosFloor = curDetPos / scale;
550 kint32 detPosRemainder = curDetPos % scale;
551 if (detPosRemainder < 0) {
553 detPosRemainder += scale;
555 int iDetPos = iDetCenter + detPosFloor;
556 double frac = detPosRemainder / dScale;
557 if (iDetPos < 0 || iDetPos >= nDet - 1)
558 errorIndexOutsideDetector (ix, iy, theta, curDetPos, iDetPos);
560 *pImCol++ += ((1.-frac) * filteredProj[iDetPos] + frac * filteredProj[iDetPos+1]);